Effects
of Family Structure and Serotonergic Genes on Affective Problems
in Italian Children

Previous
studies have investigated family structure and serotonergic
genes as separate risk factors for depression. An Italian
research team has now reported findings on the interplay between
these risk factors. To investigate this interplay, Nobile
et al. (2009) tested the effects of two-parent vs. one-parent
family structure and two serotonergic polymorphisms (TPH2
G-703T and 5-HTTLPR) on CBCL DSM-oriented Affective Problems
scale scores in Italian 10- to 14-year-olds. One sample (N
= 441) was from the Italian Project on Pre-adolescent
Mental Health (PrISMA). The second sample (N = 166)
was from a longitudinal study of emotional and behavioral
problems. For both samples, parents completed the CBCL and
a sociodemographic form that included information about marital
status. Genomic DNA was extracted from mouthwash samples.
Nobile et al. found that one-parent family structure, the
"G" variant of the TPH2 G-703T gene, and the "short"
allele of the 5-HTTLPR gene were each associated with significantly
elevated scores on the Affective Problems scale. Consistent
with genetic theory, each genetic effect was small, whereas
the family structure effect was larger than either of the
genetic effects. In testing interactions between effects of
genes and family structure, Nobile et al. found that children
obtained significantly higher Affective Problem scores if
they had the G variant of the TPH2 gene or if they had the
5-HTTLPR short allele only if they lived in one-parent
rather than two-parent families. These findings were confirmed
even after taking account of SES, Internalizing scores, and
an alternative definition of the 5-HTTLPR gene. The authors
pointed out that one-parent families may not represent exclusively
environmental risk factors, as they could be associated with
genetic risk factors The authors also pointed out that the
findings could differ in populations having different proportions
of one-parent families, which would argue for replicating
the research in additional populations. Nevertheless, the
findings certainly suggest important interactions between
effects of genes and of family structure on the problems measured
by the CBCL DSM-oriented Affective Problems scale.